contrib/less/jump.c

   1 /*
   2  * Copyright (C) 1984-2008  Mark Nudelman
   3  *
   4  * You may distribute under the terms of either the GNU General Public
   5  * License or the Less License, as specified in the README file.
   6  *
   7  * For more information about less, or for information on how to
   8  * contact the author, see the README file.
   9  */
  10
  11
  12 /*
  13  * Routines which jump to a new location in the file.
  14  */
  15
  16 #include "less.h"
  17 #include "position.h"
  18
  19 extern int jump_sline;
  20 extern int squished;
  21 extern int screen_trashed;
  22 extern int sc_width, sc_height;
  23 extern int show_attn;
  24 extern int top_scroll;
  25
  26 /*
  27  * Jump to the end of the file.
  28  */
  29         public void
  30 jump_forw()
  31 {
  32         POSITION pos;
  33         POSITION end_pos;
  34
  35         if (ch_end_seek())
  36         {
  37                 error("Cannot seek to end of file", NULL_PARG);
  38                 return;
  39         }
  40         /*
  41          * Note; lastmark will be called later by jump_loc, but it fails
  42          * because the position table has been cleared by pos_clear below.
  43          * So call it here before calling pos_clear.
  44          */
  45         lastmark();
  46         /*
  47          * Position the last line in the file at the last screen line.
  48          * Go back one line from the end of the file
  49          * to get to the beginning of the last line.
  50          */
  51         pos_clear();
  52         end_pos = ch_tell();
  53         pos = back_line(end_pos);
  54         if (pos == NULL_POSITION)
  55                 jump_loc((POSITION)0, sc_height-1);
  56         else
  57         {
  58                 jump_loc(pos, sc_height-1);
  59                 if (position(sc_height-1) != end_pos)
  60                         repaint();
  61         }
  62 }
  63
  64 /*
  65  * Jump to line n in the file.
  66  */
  67         public void
  68 jump_back(linenum)
  69         LINENUM linenum;
  70 {
  71         POSITION pos;
  72         PARG parg;
  73
  74         /*
  75          * Find the position of the specified line.
  76          * If we can seek there, just jump to it.
  77          * If we can't seek, but we're trying to go to line number 1,
  78          * use ch_beg_seek() to get as close as we can.
  79          */
  80         pos = find_pos(linenum);
  81         if (pos != NULL_POSITION && ch_seek(pos) == 0)
  82         {
  83                 if (show_attn)
  84                         set_attnpos(pos);
  85                 jump_loc(pos, jump_sline);
  86         } else if (linenum <= 1 && ch_beg_seek() == 0)
  87         {
  88                 jump_loc(ch_tell(), jump_sline);
  89                 error("Cannot seek to beginning of file", NULL_PARG);
  90         } else
  91         {
  92                 parg.p_linenum = linenum;
  93                 error("Cannot seek to line number %n", &parg);
  94         }
  95 }
  96
  97 /*
  98  * Repaint the screen.
  99  */
 100         public void
 101 repaint()
 102 {
 103         struct scrpos scrpos;
 104         /*
 105          * Start at the line currently at the top of the screen
 106          * and redisplay the screen.
 107          */
 108         get_scrpos(&scrpos);
 109         pos_clear();
 110         jump_loc(scrpos.pos, scrpos.ln);
 111 }
 112
 113 /*
 114  * Jump to a specified percentage into the file.
 115  */
 116         public void
 117 jump_percent(percent, fraction)
 118         int percent;
 119         long fraction;
 120 {
 121         POSITION pos, len;
 122
 123         /*
 124          * Determine the position in the file
 125          * (the specified percentage of the file's length).
 126          */
 127         if ((len = ch_length()) == NULL_POSITION)
 128         {
 129                 ierror("Determining length of file", NULL_PARG);
 130                 ch_end_seek();
 131         }
 132         if ((len = ch_length()) == NULL_POSITION)
 133         {
 134                 error("Don't know length of file", NULL_PARG);
 135                 return;
 136         }
 137         pos = percent_pos(len, percent, fraction);
 138         if (pos >= len)
 139                 pos = len-1;
 140
 141         jump_line_loc(pos, jump_sline);
 142 }
 143
 144 /*
 145  * Jump to a specified position in the file.
 146  * Like jump_loc, but the position need not be
 147  * the first character in a line.
 148  */
 149         public void
 150 jump_line_loc(pos, sline)
 151         POSITION pos;
 152         int sline;
 153 {
 154         int c;
 155
 156         if (ch_seek(pos) == 0)
 157         {
 158                 /*
 159                  * Back up to the beginning of the line.
 160                  */
 161                 while ((c = ch_back_get()) != '\n' && c != EOI)
 162                         ;
 163                 if (c == '\n')
 164                         (void) ch_forw_get();
 165                 pos = ch_tell();
 166         }
 167         if (show_attn)
 168                 set_attnpos(pos);
 169         jump_loc(pos, sline);
 170 }
 171
 172 /*
 173  * Jump to a specified position in the file.
 174  * The position must be the first character in a line.
 175  * Place the target line on a specified line on the screen.
 176  */
 177         public void
 178 jump_loc(pos, sline)
 179         POSITION pos;
 180         int sline;
 181 {
 182         register int nline;
 183         POSITION tpos;
 184         POSITION bpos;
 185
 186         /*
 187          * Normalize sline.
 188          */
 189         sline = adjsline(sline);
 190
 191         if ((nline = onscreen(pos)) >= 0)
 192         {
 193                 /*
 194                  * The line is currently displayed.
 195                  * Just scroll there.
 196                  */
 197                 nline -= sline;
 198                 if (nline > 0)
 199                         forw(nline, position(BOTTOM_PLUS_ONE), 1, 0, 0);
 200                 else
 201                         back(-nline, position(TOP), 1, 0);
 202 #if HILITE_SEARCH
 203                 if (show_attn)
 204                         repaint_hilite(1);
 205 #endif
 206                 return;
 207         }
 208
 209         /*
 210          * Line is not on screen.
 211          * Seek to the desired location.
 212          */
 213         if (ch_seek(pos))
 214         {
 215                 error("Cannot seek to that file position", NULL_PARG);
 216                 return;
 217         }
 218
 219         /*
 220          * See if the desired line is before or after
 221          * the currently displayed screen.
 222          */
 223         tpos = position(TOP);
 224         bpos = position(BOTTOM_PLUS_ONE);
 225         if (tpos == NULL_POSITION || pos >= tpos)
 226         {
 227                 /*
 228                  * The desired line is after the current screen.
 229                  * Move back in the file far enough so that we can
 230                  * call forw() and put the desired line at the
 231                  * sline-th line on the screen.
 232                  */
 233                 for (nline = 0;  nline < sline;  nline++)
 234                 {
 235                         if (bpos != NULL_POSITION && pos <= bpos)
 236                         {
 237                                 /*
 238                                  * Surprise!  The desired line is
 239                                  * close enough to the current screen
 240                                  * that we can just scroll there after all.
 241                                  */
 242                                 forw(sc_height-sline+nline-1, bpos, 1, 0, 0);
 243 #if HILITE_SEARCH
 244                                 if (show_attn)
 245                                         repaint_hilite(1);
 246 #endif
 247                                 return;
 248                         }
 249                         pos = back_line(pos);
 250                         if (pos == NULL_POSITION)
 251                         {
 252                                 /*
 253                                  * Oops.  Ran into the beginning of the file.
 254                                  * Exit the loop here and rely on forw()
 255                                  * below to draw the required number of
 256                                  * blank lines at the top of the screen.
 257                                  */
 258                                 break;
 259                         }
 260                 }
 261                 lastmark();
 262                 squished = 0;
 263                 screen_trashed = 0;
 264                 forw(sc_height-1, pos, 1, 0, sline-nline);
 265         } else
 266         {
 267                 /*
 268                  * The desired line is before the current screen.
 269                  * Move forward in the file far enough so that we
 270                  * can call back() and put the desired line at the
 271                  * sline-th line on the screen.
 272                  */
 273                 for (nline = sline;  nline < sc_height - 1;  nline++)
 274                 {
 275                         pos = forw_line(pos);
 276                         if (pos == NULL_POSITION)
 277                         {
 278                                 /*
 279                                  * Ran into end of file.
 280                                  * This shouldn't normally happen,
 281                                  * but may if there is some kind of read error.
 282                                  */
 283                                 break;
 284                         }
 285                         if (pos >= tpos)
 286                         {
 287                                 /*
 288                                  * Surprise!  The desired line is
 289                                  * close enough to the current screen
 290                                  * that we can just scroll there after all.
 291                                  */
 292                                 back(nline+1, tpos, 1, 0);
 293 #if HILITE_SEARCH
 294                                 if (show_attn)
 295                                         repaint_hilite(1);
 296 #endif
 297                                 return;
 298                         }
 299                 }
 300                 lastmark();
 301                 if (!top_scroll)
 302                         clear();
 303                 else
 304                         home();
 305                 screen_trashed = 0;
 306                 add_back_pos(pos);
 307                 back(sc_height-1, pos, 1, 0);
 308         }
 309 }